A window blind is mounted on a window to block sun light from directly entering a room and therefore makes the room more comfortable. When the light in the room is insufficient, the window blind can be opened to increase the brightness in the room. Further, the window blind can also be used to protect the users' privacy and decorate the room.
Conventionally, a window blind includes a blind, a transmission unit, and a plurality of cords. The transmission unit is located on a top of the blind and is connected to the cords, and the blind is connected to the cords via the transmission unit. A user can pull and control the cords for the blind to open or close in response to the movements of the transmission unit and the cords. While the conventional window blind provides the effect of adjusting indoor brightness, it has a problem in operation. Since the cords of the conventional window blind are connected to the transmission unit and the blind is connected to the cords via the transmission unit, the user has to pull the cords to open or close the blind. In the event the user pulls the cords with an excessive force or releases the cords too quickly, the blind might not be accurately stopped at the user's desired position. The user might have to pull the cords several times before the blind can be opened or closed to the desired position. Therefore, the conventional window blind has poor convenience in use.
Further, when the user intends to open or close the blind but applies an uneven force to pull the cords, the cords connected to the transmission unit tend to become tangled and could not be pulled smoothly. Therefore, additional cord accessories are needed to control the cords or prevent the cords from tangling, resulting in increased use cost of the conventional window blind.
Therefore, the conventional window blind has the following disadvantages: (1) high use cost; (2) poor convenience in use; and (3) tending to cause tangled cords and accordingly unsmooth releasing and rewinding of the cords.
It is therefore tried by the inventor to develop an improved cord winding structure for window blind to overcome the drawbacks of the conventional window blind.